Bright pupil eye-tracking system

ABSTRACT

An eye-tracking method includes enabling at least one light source of an array of light sources to emit non-visible light to illuminate an eye. The method also includes obtaining at least one image of the eye while the at least one light source is enabled. A position of the eye may then be determined based on a position of the at least one light source within the array of light sources in response to determining that the at least one image indicates a bright pupil condition when the at least one light source was enabled.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. ProvisionalApplication No. 62/983,352, entitled “Bright Pupil Eye-Tracking System”filed Feb. 28, 2020. U.S. Provisional Application No. 62/983,352 isexpressly incorporated herein by reference in their entirety.

FIELD OF DISCLOSURE

Aspects of the present disclosure relate generally to eye-trackingsystems.

BACKGROUND

Eye tracking may refer to the process of detecting the direction of auser's gaze, which may include detecting the angular orientation of theeye in 3-dimensional (3D) space. Eye tracking may further includedetecting the position and movements of the eye (e.g., the center of theeye), the torsion (i.e., the roll of the eye about the pupillary axis)of the eye, the shape of the eye, the current focal distance of the eye,the dilation of the pupil, other features of the eye's state, or somecombination thereof.

Eye tracking systems may be utilized in a variety of contexts, such asmedical research or diagnosis, human-computer interaction, etc. In somecontexts, such as with head mounted displays (HMDs), it may beadvantageous for the HMD to determine the location of the eye of theuser and/or determine where the eyes of the user are focusing to alterthe content being presented to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive aspects of the present disclosure aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified.

FIG. 1A illustrates an example eye-tracking system, in accordance withaspects of the present disclosure.

FIG. 1B illustrates another example eye-tracking system, in accordancewith aspects of the present disclosure.

FIG. 2 illustrates an array of light sources and the correspondingimages of an eye captured when at least one of the light sources areenabled, in accordance with aspects of the present disclosure.

FIG. 3A illustrates an array of light sources and the correspondingimages of an eye captured when a grouping of light sources are enabled,in accordance with aspects of the present disclosure.

FIG. 3B illustrates an array of light sources and the correspondingimages of an eye captured with individual light sources of a groupingare enabled, in accordance with aspects of the present disclosure.

FIG. 4 illustrates a computing device, in accordance with aspects of thepresent disclosure.

FIG. 5 is a flow chart illustrating a process of eye-tracking, inaccordance with aspects of the present disclosure.

FIG. 6 is a flow chart illustrating another process of eye-tracking thatincludes enabling a first and a second light source, in accordance withaspects of the present disclosure.

FIG. 7 is a flow chart illustrating a process of eye-tracking thatincludes enabling a first and a second grouping of light sources, inaccordance with aspects of the present disclosure.

FIG. 8 illustrates a head mounted display (HMD), in accordance withaspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects and embodiments are disclosed in the followingdescription and related drawings to show specific examples relating toan eye-tracking method and system. Alternate aspects and embodimentswill be apparent to those skilled in the pertinent art upon reading thisdisclosure and may be constructed and practiced without departing fromthe scope or spirit of the disclosure. Additionally, well-known elementswill not be described in detail or may be omitted so as to not obscurethe relevant details of the aspects and embodiments disclosed herein.

In some implementations of the disclosure, the term “near-eye” may bedefined as including an element that is configured to be placed within50 mm of an eye of a user while a near-eye device is being utilized.Therefore, a “near-eye optical element” or a “near-eye system” wouldinclude one or more elements configured to be placed within 50 mm of theeye of the user.

In aspects of this disclosure, visible light may be defined as having awavelength range of approximately 380 nm-700 nm. Non-visible light maybe defined as light having wavelengths that are outside the visiblelight range, such as ultraviolet light and infrared light. Infraredlight having a wavelength range of approximately 700 nm-1 mm includesnear-infrared light. In aspects of this disclosure, near-infrared lightmay be defined as having a wavelength range of approximately 700 nm-1.4μm.

FIG. 1A illustrates an example eye-tracking system 100A, in accordancewith aspects of the present disclosure. The illustrated example ofeye-tracking system 100A includes an array of light sources 102A-102G, alayer 104, beam shaping optics 106A-106G, an optical element 108, anoptical combiner 110, a camera 120, and a computing device 122. Alsoshown in FIG. 1A is an eye 114 that includes a fundus 112, a pupil 118,and a pupil plane 116.

As shown in FIG. 1A, the light sources 102A-102G are disposed on layer104. Layer 104 may be a transparent substrate, such as glass or plastic.In one example, the light sources 102A-102G may be encapsulated withinthe transparent substrate. The transparent substrate may be transmissiveto visible light (e.g. 400 nm-750 nm) and may be configured to be placedon a display plane of an electronic or optical display layer (e.g., aliquid crystal display (LCD), an organic light emitting diode (OLED)display, a micro-LED display, a waveguide, etc.) that is configured togenerate display light for presentation to the user. In another example,layer 104 is, itself, the electronic or optical display layer, wherelight sources 102A-102G are disposed on the display layer, interspersedwithin display light that is generated by the display layer (e.g.,within the field of view of the user).

Each light source 102A-102G may be a micro light emitting diode(micro-LED), an edge emitting LED, a vertical cavity surface emittinglaser (VCSEL) diode, or a Superluminescent diode (SLED). In addition,each light source 102A-102G may be individually enabled to emitnon-visible light 107 to illuminate the eye 114. In some examples,non-visible light 107 is infrared light or near-infrared light. In someaspects, each light source 102A-102G is arranged on layer 104 in atwo-dimensional (2D) array of columns and rows. In some examples, eachlight source 102A-102G may be referred to as a point light source, whereonly one of the light sources 102A-102G are enabled at a time to emitnon-visible light 107 (e.g., in the illustrated example of FIG. 1A, onlya single light source 102G is currently enabled to emit non-visiblelight 107).

The illustrated example of FIG. 1A also illustrates a plurality of beamshaping optics 106A-106G. Each beam shaping optic 106A-106G may bedisposed on a corresponding light source 102A-102G to direct thenon-visible light emitted by each light source along a respectiveoptical axis. Thus, in some aspects, each light source 102A-102G may beconfigured, by way of a respective beam shaping optic 106A-106G, to emitnon-visible light 107 along a different optical axis. For example, beamshaping optic 106A may be configured to direct non-visible lightgenerated by light source 102A along a first optical axis, whereas beamshaping optic 106B may be configured to direct non-visible lightgenerated by light source 102B along a second (i.e., different) opticalaxis. In some examples, each of the beam shaping optics 106A-106G mayalso be configured to collimate the non-visible light 107 generated by arespective light source 102A-102G.

As shown in FIG. 1A, the eye-tracking system 100A also includes anoptical element 108 that is disposed between the beam shaping optics106A-106G and an eyeward side 103 of the eye-tracking system 100A. FIG.1A also illustrates an optical combiner 110 that is disposed between thelight sources 102A-102G and the eyeward side 103, and in particular maybe disposed between the optical element 108 and the eyeward side 103. Insome examples, optical element 108 includes one or more lenses that areconfigured to receive the collimated non-visible light 107 and to focusthe collimated non-visible light 107 through the optical combiner 110 tothe pupil plane 116 of the eye 114. Thus, in some examples, the opticalelement 108 provides a “Maxwellian view” of the non-visible light 107.As shown in FIG. 1A, the non-visible light 107 then expands as it exitsthe pupil 118 towards to back of the eye 114 to illuminate a large areaof the fundus 112.

In some aspects, the optical combiner 110 is configured to receivereflected non-visible light 109 (having the wavelength emitted by thelight sources 102A-102G) that is reflected/scattered by the fundus 112of eye 114 and to direct the reflected non-visible light 109 to thecamera 120. The camera 120 may be located in different positions thanthe positions illustrated. In some aspects, the optical combiner 110 istransmissive to visible light (e.g. approximately 400 nm-700 nm), suchas scene light (e.g., from the environment) that is incident on thebackside 105 of the eye-tracking system 100A. Even still, in someexamples, the optical combiner 110 is transmissive to visible light thatgenerated by a display layer (e.g., layer 104). In some examples, theoptical combiner 110 may be configured as a holographic optical element(HOE) or a volume hologram that may include one or more Bragg gratingsfor directing the reflected non-visible light 109 toward the camera 120.In some examples, the optical combiner 110 includes apolarization-selective volume hologram (a.k.a. polarized volumehologram) that diffracts (in reflection) a particular polarizationorientation of incident light having a particular wavelength towardcamera 120 while passing other polarization orientations.

The camera 120 is configured to generate one or more images 123 of theeye 114, where the images 123 are of the reflected non-visible light109. In some examples, camera 120 may be configured to filter out lightthat is other than the non-visible light 107/reflected non-visible light109 such that the camera 120 only images the wavelength of the reflectednon-visible light 109.

In some examples, the computing device 122 may be configured todetermine eye-tracking information (e.g., location, orientation, gazeangle, etc.) of the eye 114 based on images 123 captured by the camera120. As will be described in more detail below, the computing device 122may then process the images 123 to detect a bright pupil condition todetermine eye-tracking information (e.g., position, orientation, gazeangle, etc. of the eye 114). For example, the computing device 122 maydetermine whether the eye 114 is looking in the straight, left, right,upwards, or downwards direction.

In some embodiments, the computing device 122 may include a light sourcecontrol module that is communicatively coupled to the array of lightsources 102A-102G. As discussed above, each of the light sources102A-102G may emit non-visible light 107 along a respective opticalaxis. If the eye 114 is misaligned with a currently-enabled light source102A-102G, then the pupil 118 of the eye may vignette the non-visiblelight 107 which may reduce or prevent the light from reaching the fundus112, which will darken the appearance of the pupil 118 in the resultantimage 123. However, if the eye 114 is aligned with the currently-enabledlight source 102A-102G (e.g., along the same optical axis as thenon-visible light 107 being emitted), then the pupil 118 will appearbrighter in the resultant image 123.

Accordingly, the control module of computing device 122 may generate oneor more control signals 124 to selectively enable at least one of thelight sources 102A-102G and analyze the resultant images 123 to detect abright pupil condition. If an image 123 that was captured while aparticular light source (e.g., light source 102G) was enabled indicatesa bright pupil condition, then the computing device 122 may thendetermine a position/gaze angle of the eye 114 based on a position ofthat light source (e.g., light source 102G) within the array of lightsources.

As mentioned above, the beam shaping optics 106A-106G may be configuredto collimate the non-visible light 107 that is emitted by the lightsources 102A-102G, where optical element 108 then focuses the collimatednon-visible light onto the pupil plane 116. However, in other examplesof the present disclosure, the beam shaping optics 106A-106G thatcollimate the non-visible light may be omitted. For example, FIG. 1Billustrates another example eye-tracking system 100B, in accordance withaspects of the present disclosure. In the illustrated example of FIG.1B, the non-visible (and non-collimated) light 107 emitted by the lightsource 102G is received by optical element 108. In this example, theoptical element 108 may then collimate the non-visible light and directthe collimated non-visible light to the eye 114. The eye 114 thenfocuses the collimated non-visible light (e.g., by way of the lens ofthe eye 114) onto the fundus 112. In this example, the fundus 112 mayact as a retroreflector where the reflected non-visible light isreflected back at an angle that is substantially the same as the anglethat the non-visible light is incident upon the fundus 112. Similar tothe example of FIG. 1A, the reflected non-visible light 109 is receivedby the optical combiner 110, which then directs the reflectednon-visible light 109 to the camera 120 to generate the images 123.

FIG. 2 illustrates an array of light sources 206 and the correspondingimages 202A-202G of an eye captured when at least one of the lightsources are enabled, in accordance with aspects of the presentdisclosure. The array of light sources 206 is one possible example ofthe array of light sources 102A-102G of FIGS. 1A and 1B. Similarly, theimages 202A-202G are possible examples of the images 123. As discussedabove, each of the light sources of the array of light sources 206 maybe individually enabled to emit non-visible light to illuminate the eye,where a corresponding image may then be captured of the eye while thelight source is enabled. By way of example, FIG. 2 illustrates an image202A that was captured when light source 208A was enabled, image 202B isan image of the eye when light source 208B was enabled, image 202C is animage of the eye when light source 208C was enabled, image 202D is animage of the eye when light source 208D was enabled, image 202E is animage of the eye when light source 208E was enabled, image 202F is animage of the eye when light source 208F was enabled, image 202G is animage of the eye when light source 208G was enabled, and so on. Theimages captured by the camera (e.g., camera 120 of FIG. 1A) may then beanalyzed by a computing device (e.g., computing device 122 of FIG. 1A).In one example, analyzing the images 202A-202G includes determining ifany of the images indicate a bright pupil condition. In the illustratedexample of FIG. 2, image 202E indicates a bright pupil condition of thepupil 204. In response to determining that an image indicates a brightpupil condition, the computing device determines that the eye wasaligned with the light source that was enabled when the image wasobtained (e.g., the eye was aligned with light source 208E when image202E was captured). The computing device may then determine the positionof the eye based on a known position of the light source 208E within thearray 206. In some examples, determining the position of the eyeincludes translating the position of the light source 208E to acalculated eye position and/or gaze angle.

In some examples, determining whether a bright pupil condition existsincludes comparing a brightness of the pupil 204 in one image to thebrightness of the pupil 204 in another image. In some aspects, this mayinclude utilizing one or more computer-vision techniques to identify apupil region of each image and determining a brightness of the pupilregion (e.g., average brightness of all pixels within the pupil region).The determined brightness of the pupil region may then be compared withthe brightness determined in other images, where the image with thebrightest pupil region is determined to indicate a bright pupilcondition.

In other examples, the bright pupil condition may be determined bycomparing the brightness of the pupil region of an image with abrightness threshold. That is, in this example, rather than comparingimages together, the brightness of the pupil region of one image may becompared against a fixed or dynamically-created threshold that indicatesthe bright pupil condition.

In some aspects, each light source of the array of light sources 206 maybe individually enabled and a corresponding image captured. However, inother examples, two or more groupings of light sources may be enabled,where corresponding images are obtained to determine whether the eye isaligned with a particular grouping of light sources. By way of example,FIG. 3A illustrates the array of light sources 206 and the correspondingimages 302A and 302B of an eye captured when a grouping of light sourcesare enabled, in accordance with aspects of the present disclosure. Asshown in FIG. 3A, image 302A is an image of the eye captured when afirst grouping 304 of light source were enabled, whereas image 302B isan image of the eye captured when a second grouping 306 of light sourceswere enabled. Although FIG. 3A illustrates only two groupings of lightsources, other embodiments may include multiple groupings of the arrayof light sources 206, including two or more.

In some examples, enabling a grouping of light sources includessimultaneously enabling multiple light sources of the array of lightsources 206, where the captured image includes an image of the eye whenall of the light sources in the grouping were enabled. The resultantimages 302A and 302B may then be analyzed (e.g., by computing device122) to determine whether a bright pupil condition exists, either bycomparing the brightness of the pupil 204 of image 302A with thebrightness of the pupil 204 of image 302B, or by comparing thebrightness of the pupil 204 in each image with the brightness threshold.In the illustrated example, image 302B indicates the bright pupilcondition.

An image that indicates a bright pupil condition when a grouping oflight sources were enabled means that one of the light sources includedin the grouping of light sources 206 is aligned with the eye. Thus, insome examples, each light source of that grouping (e.g., grouping 306 ofFIG. 3A) may then be individually enabled (and a corresponding imagecaptured) to determine the particular light source that caused thebright pupil condition.

For example, FIG. 3B illustrates the array of light sources 206 and thecorresponding images 302 x-302 z of an eye captured when individuallight sources of grouping 306 are enabled, in accordance with aspects ofthe present disclosure Image 302 x is an image of the eye that wascaptured when light source 308A was enabled, image 302 y is an image ofthe eye when light source 308B was enabled, and image 302 z is an imageof the eye when light source 308C was enabled. Although FIG. 3B onlyillustrates three images 302 x-302 y, as mentioned above, aspects of thepresent disclosure may include individually enabling each of the lightsources included in the grouping 306. As shown in FIG. 3B, image 302 yindicates a bright pupil condition, where the computing device may thendetermine a position of the eye based on the position of light source308B within the array of light sources 206.

FIG. 4 illustrates a computing device 402, in accordance with aspects ofthe present disclosure. The illustrated example of computing device 402is shown as including a communication interface 404, one or moreprocessors 406, hardware 408, and a memory 410. The computing device 402of FIG. 4 is one possible implementation of the computing device 122 ofFIG. 1A.

The communication interface 404 may include wireless and/or wiredcommunication components that enable the computing device 402 totransmit data to and receive data from other devices/components. Thehardware 408 may include additional hardware interface, datacommunication, or data storage hardware. For example, the hardwareinterfaces may include a data output device, and one or more data inputdevices.

The memory 410 may be implemented using computer-readable media, such ascomputer storage media. In some aspects, computer-readable media mayinclude volatile and/or non-volatile, removable and/or non-removablemedia implemented in any method or technology for storage of informationsuch as computer-readable instructions, data structures, programmodules, or other data. Computer-readable media includes, but is notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, digital versatile disks (DVD), high-definition multimedia/datastorage disks, or other optical storage, magnetic cassettes, magnetictape, magnetic disk storage or other magnetic storage devices, or anyother non-transmission medium that can be used to store information foraccess by a computing device.

The processors 406 and the memory 410 of the computing device 402 mayimplement a light source control module 412, a camera interface module414, a bright pupil detection module 416, and a position determinationmodule 418. The light source control module 412, camera interface module414, bright pupil detection module 416, and the position determinationmodule 418 may include routines, program instructions, objects, and/ordata structures that perform particular tasks or implement particularabstract data types. The memory 410 may also include a data store (notshown) that is used by the light source control module 412, camerainterface module 414, bright pupil detection module 416, and/or theposition determination module 418.

The light source control module 412 may be configured to generate one ormore control signals (e.g., control signals 124 of FIG. 1A) to enableand/or disable one or more of the light sources included in the array oflight sources 102A-102G. The camera interface module 414 may beconfigured to receive images (e.g., images 123 of FIG. 1A). The camerainterface module 414 may optionally be configured to trigger the camera120 to capture one or more images in response to the light sourcecontrol module 412 enabling a light source of the array of lightsources. The bright pupil detection module 416 is configured to analyzeone or more images to determine whether an image indicates the brightpupil condition. As mentioned above, the bright pupil detection module416 may implement one or more computer-vision techniques to identify apupil region and to determine a corresponding brightness of the pupilregion. The bright pupil detection module 416 may detect the brightpupil condition by comparing the brightness of the pupil region amongtwo or more images or, alternatively, may detect the bright pupilcondition by comparing the brightness of the pupil region on an imagewith the brightness threshold. In response to the bright pupil detectionmodule 416 detecting the bright pupil condition, the positiondetermination module 418 may determine a position of the eye based on aposition of the light source that was enabled for the image thatindicates such a bright pupil condition. As mentioned above, theposition of the eye may be determined by translating the position of thelight source to a calculated eye-position and/or gaze angle.

FIG. 5 is a flow chart illustrating a process 500 of eye-tracking, inaccordance with aspects of the present disclosure. Process 500 is onepossible process of eye-tracking performed by the eye-tracking system100A of FIG. 1A. In a process block 502, the computing device 122 ofFIG. 1A may generate a control signal 124 to enable at least one lightsource 102G of the array of light sources 102A-102G to emit non-visiblelight 107 to illuminate an eye 114. In a process block 504, thecomputing device 122 may obtain (e.g., receive) at least one image 123of the eye 114 that was captured by the camera 120 while the at leastone light source 102G was enabled. Next, in a process block 508, thecomputing device 122 may determine a position of the eye 114 based on aposition of the at least one light source 102G within the array of lightsources 102A-102G in response to determining that the image 123indicates a bright pupil condition.

FIG. 6 is a flow chart illustrating another process 600 of eye-trackingthat includes enabling a first and a second light source, in accordancewith aspects of the present disclosure. Process 600 is described withreference to FIG. 2. In a process block 602 a first light source 208A ofthe array of light sources 206 is enabled to emit non-visible light toilluminate an eye. In a process block 604, a first image 202A isobtained that is an image of the eye captured when the first lightsource 208A was enabled. Next, in a process block 606 a second lightsource 208E is enabled to emit non-visible light to illuminate the eye(e.g., and the first light source 208A is disabled). Process block 608includes obtaining the image 202E that was captured by the camera (e.g.,camera 120) while the second light source 208E was enabled.

In a decision block 610, the computing device (e.g., computing device122) determines whether the pupil 204 in the first image 202A isbrighter than the pupil 204 in the second image 202E. If the pupil 204in the first image 202A is determined to be brighter than the pupil 204in the second image 202E, then process 600 proceeds to process block612, where the computing device determines the position of the eye basedon the position of the first light source 208A within the array of lightsources 206. If, however, in decision block 610, it is determined thatthe pupil 204 in the first image 202A is not brighter than the pupil 204in the second image 202E (i.e., the pupil 204 in the second image 202Eis brighter), then process 600 proceeds to process block 614 where theposition of the eye is determined based on the position of the secondlight source 208E with the array of light sources 206.

Although process 600 is described above with reference to the enablingof only two of the light sources (and obtaining a corresponding twoimages), as described above, aspects of the present disclosure mayinclude individually enabling two or more of the light sources includedin the array of light sources 102A-102G, where the brightness's of eachof the obtained images are compared to one another to determine whichimage indicates the bright pupil condition.

FIG. 7 is a flow chart illustrating a process 700 of eye-tracking thatincludes enabling a first and a second grouping of light sources, inaccordance with aspects of the present disclosure. Process 700 isdescribed with reference to FIGS. 3A and 3B.

In a process block 702 a first grouping 304 of light sources is enabledto emit non-visible light to illuminate an eye. In a process block 704,a first image 302A is obtained that is an image of the eye while alllight sources included in the first grouping 304 were simultaneouslyenabled. In a process block 706, a second grouping 306 of light sourcesis enabled to emit the non-visible light. Process block 708 includesobtaining the second image 302B that is an image of the eye while alllight sources included in the second grouping 306 were simultaneouslyenabled (e.g., and light sources of the first grouping 304 weredisabled).

Next, in decision block 710, the computing device (e.g., computingdevice 122) determines whether the pupil 204 in the first image 302A isbrighter than the pupil 204 in the second image 302B. If the pupil 204in the first image 302A is determined to be brighter than the pupil 204in the second image 302B, then process 700 proceeds to process block712, where each light source within the first grouping 304 areindividually enabled and respective images of the eye are obtained(e.g., captured by camera 120). In a process block 714, the computingdevice then determines a position of the eye based on a position of alight source of the first grouping 304 that corresponds to an image(i.e., obtained in process block 712) that indicates a bright pupilcondition.

Returning to decision block 710, if the pupil 204 in the first image302A is not brighter than the pupil 204 in the second image 302B, thenprocess 700 proceeds to process block 716 where each of the lightsources included in the second grouping 306 are individually enabled andrespective images of the eye are obtained. In a process block 718, thecomputing device may then determine the position of the eye based on aposition of a light source of the second grouping 306 that correspondsto an image (i.e., obtained in process block 716) that indicates thebright pupil condition.

In some implementations, aspects of the present disclosure may beutilized in a head mounted device, such as a virtual reality (VR) oraugmented reality (AR) device. In some aspects, a head mounted devicemay incorporate an eye-tracking system to enhance a user's viewingexperience. Eye-tracking, may in some instances, be aided by determiningthe position and/or movement of the eye. For example, when the gazeangle is determined, a virtual image presented to a user by a display ofa head mounted device may be adjusted in response to the determined gazeangle.

By way of example, FIG. 8 illustrates a head-mounted display (HMD) 800,in accordance with aspects of the present disclosure. An HMD, such asHMD 800, is one type of head mounted device, typically worn on the headof a user to provide artificial reality content to a user. Artificialreality is a form of reality that has been adjusted in some mannerbefore presentation to the user, which may include, e.g., virtualreality (VR), augmented reality (AR), mixed reality (MR), hybridreality, or some combination and/or derivative thereof. The illustratedexample of HMD 800 is shown as including a viewing structure 840, a topsecuring structure 841, a side securing structure 842, a rear securingstructure 843, and a front rigid body 844. In some examples, the HMD 800is configured to be worn on a head of a user of the HMD 800, where thetop securing structure 841, side securing structure 842, and/or rearsecuring structure 843 may include a fabric strap including elastic aswell as one or more rigid structures (e.g., plastic) for securing theHMD 800 to the head of the user. HMD 800 may also optionally include oneor more earpieces 820 for delivering audio to the ear(s) of the user ofthe HMD 800.

The illustrated example of HMD 800 also includes an interface membrane818 for contacting a face of the user of the HMD 800, where theinterface membrane 818 functions to block out at least some ambientlight from reaching to the eyes of the user of the HMD 800.

Example HMD 800 may also include a chassis for supporting hardware ofthe viewing structure 840 of HMD 800 (chassis and hardware notexplicitly illustrated in FIG. 8). The hardware of viewing structure 840may include any of processing logic, wired and/or wireless datainterface for sending and receiving data, graphic processors, and one ormore memories for storing data and computer-executable instructions. Inone example, viewing structure 840 may be configured to receive wiredpower and/or may be configured to be powered by one or more batteries.In addition, viewing structure 840 may be configured to receive wiredand/or wireless data including video data.

Viewing structure 840 may include a display system having one or moreelectronic displays for directing light to the eye(s) of a user of HMD800. The display system may include one or more of a liquid crystaldisplay (LCD), an organic light emitting diode (OLED) display, amicro-LED display, etc. for emitting light (e.g., content, images,video, etc.) to a user of HMD 800. The viewing structure 840 may alsoinclude an optical assembly that is configured to receive the imagelight from the display system and generate a virtual image (e.g., bycollimating the image light) for viewing by an eye of a wearer of theHMD 800.

In some examples, viewing structure includes an eye-tracking system 845for tracking movements and/or determining a position of the user's eye.The eye-tracking system 845 may be implemented by way of any of theembodiments discussed herein, including eye-tracking system 100A of FIG.1A.

Embodiments of the invention may include or be implemented inconjunction with an artificial reality system. Artificial reality is aform of reality that has been adjusted in some manner beforepresentation to a user, which may include, e.g., a virtual reality (VR),an augmented reality (AR), a mixed reality (MR), a hybrid reality, orsome combination and/or derivatives thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,and any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer). Additionally, in some embodiments, artificial realitymay also be associated with applications, products, accessories,services, or some combination thereof, that are used to, e.g., createcontent in an artificial reality and/or are otherwise used in (e.g.,perform activities in) an artificial reality. The artificial realitysystem that provides the artificial reality content may be implementedon various platforms, including a head-mounted display (HMD) connectedto a host computer system, a standalone HMD, a mobile device orcomputing system, or any other hardware platform capable of providingartificial reality content to one or more viewers.

The above description of illustrated embodiments of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific embodiments of, and examples for, the invention aredescribed herein for illustrative purposes, various modifications arepossible within the scope of the invention, as those skilled in therelevant art will recognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific embodimentsdisclosed in the specification. Rather, the scope of the invention is tobe determined entirely by the following claims, which are to beconstrued in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. An eye-tracking method, comprising: enabling atleast one light source of an array of light sources to emit non-visiblelight to illuminate an eye; obtaining at least one image of the eyewhile the at least one light source is enabled; and determining aposition of the eye based on a position of the at least one light sourcewithin the array of light sources in response to determining that the atleast one image indicates a bright pupil condition when the at least onelight source was enabled.
 2. The eye-tracking method of claim 1, wheredetermining that the at least one image indicates the bright pupilcondition comprises: comparing a brightness of the pupil in the at leastone image with a brightness of the pupil in another image thatcorresponds to when another light source of the array of light sourcesis enabled to emit non-visible light to illuminate the eye.
 3. Theeye-tracking method of claim 1, wherein determining that the at leastone image indicates the bright pupil condition comprises: comparing abrightness of the pupil in the at least one image with a brightnessthreshold.
 4. The eye-tracking method of claim 1, further comprising:enabling a first light source of the array of light sources to emitnon-visible light to illuminate the eye; obtaining a first image of theeye while the first light source is enabled; enabling a second lightsource of the array of light sources to emit non-visible light toilluminate the eye; obtaining a second image of the eye while the secondlight source is enabled; and determining the position of the eye basedon a position of the first light source within the array of lightsources in response to determining that the pupil of the eye in thefirst image is brighter than the pupil of the eye in the second image.5. The eye-tracking method of claim 4, further comprising: determiningthe position of the eye based on a position of the second light sourcewithin the array of light sources in response to determining that thepupil of the eye in the second image is brighter than the pupil of theeye in the first image.
 6. The eye-tracking method of claim 1, whereinthe non-visible light comprises infrared or near-infrared light.
 7. Theeye-tracking method of claim 1, further comprising: enabling a firstgrouping of light sources of the array of light sources; obtaining afirst image of the eye while the first grouping of light sources areenabled; enabling a second grouping of light sources of the array oflight sources; obtaining a second image of the eye while the secondgrouping of light sources are enabled; comparing a brightness of thepupil in the first image with a brightness of the pupil in the secondimage; and determining that the pupil is aligned with the first groupingof light sources in response to determining that the pupil in the firstimage is brighter than the pupil in the second image.
 8. Theeye-tracking method of claim 7, further comprising: individuallyenabling each light source of the first grouping in response todetermining that the pupil is aligned with the first grouping of lightsources; obtaining respective images of the eye while each light sourceof the first grouping of light sources are individually enabled; anddetermining that one image of the respective images indicates the brightpupil condition, wherein determining the position of the eye is based ona position of one of the light sources included in the first groupingthat corresponds to the one image that indicates the bright pupilcondition.
 9. The eye-tracking method of claim 7, further comprising:determining that the pupil is aligned with the second grouping of lightsources in response to determining that the pupil in the second image isbrighter than the pupil in the first image; individually enabling eachlight source of the second grouping in response to determining that thepupil is aligned with the second grouping of light sources; obtainingrespective images of the eye while each light source of the secondgrouping of light sources is individually enabled; and determining thatone image of the respective images indicates the bright pupil condition,wherein determining the position of the eye is based on a position ofone of the light sources included in the second grouping thatcorresponds to the one image that indicates the bright pupil condition.10. An eye-tracking system, comprising: an array of light sources,wherein each light source of the array of light sources is configured tobe selectively enabled to emit non-visible light to an eyeward side ofthe eye-tracking system to illuminate an eye; a camera configured tocapture images of the eye based on the non-visible light; and acomputing device communicatively coupled to the array of light sourcesand the camera, wherein the computing device comprises: a light sourcecontrol module configured to enable at least one light source of thearray of light sources; a camera interface module configured to obtainat least one image of the eye, captured by the camera while the at leastone light source was enabled; a bright pupil detection module configuredto detect whether the at least one image indicates a bright pupilcondition; and a position determination module configured to determine aposition of the eye based on a position of the at least one light sourcewithin the array of light sources in response to the bright pupildetection module determining that the at least one image indicates thebright pupil condition.
 11. The eye-tracking system of claim 10, wherethe bright pupil detection module is configured to: compare a brightnessof the pupil in the at least one image with a brightness of the pupil inanother image that corresponds to when another light source of the arrayof light sources is enabled to emit non-visible light to illuminate theeye.
 12. The eye-tracking system of claim 10, wherein the bright pupildetection module is configured to: compare a brightness of the pupil inthe at least one image with a brightness threshold.
 13. The eye-trackingsystem of claim 10, wherein the non-visible light comprises infrared ornear-infrared light.
 14. The eye-tracking system of claim 10, furthercomprising: an optical combiner disposed between the array of lightsources and an eyeward side of the eye-tracking system, wherein theoptical combiner is configured to receive reflected non-visible lightthat is reflected by the eye to direct the reflected non-visible lightto the camera to generate the images of the eye.
 15. The eye-trackingsystem of claim 14, wherein the array of light sources comprises atransparent substrate and wherein each light source of the array oflight sources is disposed on the transparent substrate.
 16. Theeye-tracking system of claim 10, further comprising a plurality of beamshaping optics, each beam shaping optic of the plurality of beam shapingoptics disposed on a corresponding light source of the array of lightsources to direct the non-visible light emitted by each respective lightsource along a corresponding optical axis.
 17. The eye-tracking systemof claim 16, wherein each beam shaping optic of the plurality of beamshaping optics are configured to collimate the non-visible light intocollimated non-visible light.
 18. The eye-tracking system of claim 17,further comprising: an optical element disposed between the plurality ofbeam shaping optics and the eyeward side of the eye-tracking system tofocus the collimated non-visible light onto a pupil plane of the eye.19. A head-mounted display (HMD), comprising: an array of light sources,wherein each light source of the array of light sources is configured tobe selectively enabled to emit non-visible light to an eyeward side ofthe HMD to illuminate an eye; a camera configured to capture images ofthe eye; an optical combiner disposed between the array of light sourcesand the eyeward side, wherein the optical combiner is configured toreceive reflected non-visible light that is reflected by the eye and todirect the reflected non-visible light to the camera to generate theimages of the eye; a display layer disposed between the optical combinerand a backside of the HMD, the display layer configured to providedisplay light that propagates through the optical combiner to theeyeward side of the HMD; and a computing device communicatively coupledto the array of light sources and the camera, wherein the computingdevice comprises: a light source control module configured to enable atleast one light source of the array of light sources; a camera interfacemodule configured to obtain at least one image of the eye, captured bythe camera while the at least one light source was enabled; a brightpupil detection module configured to detect whether the at least oneimage indicates a bright pupil condition; and a position determinationmodule configured to determine a position of the eye based on a positionof the at least one light source within the array of light sources inresponse to the bright pupil detection module determining that the atleast one image indicates the bright pupil condition.
 20. The HMD ofclaim 19, wherein each light source of the array of light sources isdisposed on the display layer.